sim.updateParticles script

local lastparticle = -1
local overlay = false
local lastkey = {}
local dokeypress

local function step()
    if tpt.set_pause() == 0 then
        lastparticle = -1
    end
    if overlay then
        for i in sim.parts() do
            if i <= lastparticle then
                tpt.drawpixel(math.floor(tpt.get_property("x", i)+.5), math.floor(tpt.get_property("y", i)+.5), 0, 0, 0, 150)
            else
                break
            end
        end
    end
    if lastkey["time"] and lastkey["time"] < socket.gettime() then
        dokeypress(lastkey["key"], lastkey["nkey"], lastkey["modifier"], lastkey["event"])
        lastkey["time"] = socket.gettime()+.1
    end
end
tpt.register_step(step)

--replicate TPT's life decreasing
local function decreaselife()
    for i in sim.parts() do
        local life = tpt.get_property("life", i)
        local properties = elem.property(tpt.get_property("type", i), "Properties")
        if life > 0 and bit.band(properties, elem.PROP_LIFE_DEC) ~= 0 then
            if life == 1 and bit.band(properties, bit.bor(elem.PROP_LIFE_KILL_DEC,elem.PROP_LIFE_KILL)) ~= 0 then
                sim.partKill(i)
            else
                tpt.set_property("life", life-1, i)
            end
        elseif life <= 0 and bit.band(properties, elem.PROP_LIFE_KILL) ~= 0 then
            sim.partKill(i)
        end
    end
end

function dokeypress(key, nkey, modifier, event)
    if event == 1 and key == 'f' then
        if bit.band(modifier, 0x300) ~= 0 then
            overlay = not overlay
            return false
        elseif bit.band(modifier, 0xC0) ~= 0 then --ctrl is pressed
            lastparticle = lastparticle + 1
            if lastparticle >= sim.XRES*sim.YRES then
                print("reached the end of the particles")
                lastparticle = -1
            else
                if lastparticle == -1 then
                    print("decreasing particle life")
                    decreaselife()
                end
                while lastparticle < sim.XRES*sim.YRES and tpt.get_property("type", lastparticle) == 0 do
                    lastparticle = lastparticle + 1
                end
                sim.updateParticles(lastparticle, lastparticle)
            end
            return false
        elseif bit.band(modifier, 0x3) ~= 0 then --shift is pressed
            local mousex, mousey = sim.adjustCoords(tpt.mousex, tpt.mousey)
            local i = sim.pmap(mousex, mousey)
            if i then
                if i > lastparticle then
                    print("advancing from particle #"..(lastparticle+1).." to particle #"..i)
                    sim.updateParticles(lastparticle+1, i)
                    lastparticle = i
                else
                    print("#"..lastparticle.." has already been updated")
                end
            else
                print("advancing to end (particles #"..(lastparticle+1).." to #"..(sim.XRES*sim.YRES-1)..")")
                sim.updateParticles(lastparticle+1, sim.XRES*sim.YRES-1)
                lastparticle = -1
            end
            return false
        else
            lastparticle = -1
        end
    end
end

local function keypress(key, nkey, modifier, event)
    if event == 1 then
        lastkey = {["key"] = key, ["nkey"] = nkey, ["modifier"] = modifier, ["event"] = event, ["time"] = socket.gettime()+.5}
    else
        lastkey = {}
    end
    return dokeypress(key, nkey, modifier, event)
end
tpt.register_keypress(keypress)